A watch of this type is described, for example, in patent CH 338 150. A mechanical movement, of the traditional type, is topped by a U-shaped stirrup whereof the base is passed through by the cannon-pinion. This drives two vertical wheels mounted pivoting in the branches of the stirrup and turning at speeds whereof the ratio is that of the angular speeds of the hands of a traditional watch. These two wheels are respectively engaged with the toothings presented by two endless ribbons arranged next to each other, around the movement, and one bearing the minute information, the other the hour information.
This type of construction does, however, suffer two main drawbacks. First, the power and the energy of the spring contained in the barrel risk being insufficient to drive the ribbon over an acceptable period of time. Secondly, the watch is very thick because it is made up of the stack of a movement, the drive mechanism of the ribbon and a sufficient space to allow the latter part to revolve around the assembly.